1. Field of the Invention
The present invention generally relates to a communication apparatus such as mobile or portable telephone equipment, and relates, more particularly, to communication apparatus and control method making use of speech recognition technique.
2. Description of the Related Art
In the field of mobile or portable telephone system of Japan, Personal Digital Cellular (PDC) system is currently mainstream, wherein Vector Sum Excited Linear Prediction (VSELP) system is employed as full-rate speech coding system and Pitch synchronous innovation Code Excited Linear Prediction (PSI-CELP) system is employed as half-rate speech coding system. According to these speech coding systems, an input speech signal is compared with a code stored in a speech code book prepared in advance so that a code closest to the input speech signal is selected, and the selected code is transmitted to the other party. At the code receiving side, the received code is reproduced as a speech signal by using the same code book prepared at this side.
There has been proposed a portable telephone of the PDC system having a calling restriction function for enabling only the owner of the portable telephone to make a call. Particularly, there are disclosed telephone apparatuses for performing the calling restriction based on speech recognition in Japanese Patent Application Laid-open Publication No. 61-245785 and in Japanese Patent Application Laid-open Publication No.2-34078, respectively.
For example, according to a telephone apparatus equipped with a calling restriction device as disclosed in the publication No.2-34078, a vocalized password is registered in advance and the calling restriction is removed when the same password has been input in the same speech feature.
However, according to the above-described techniques, no mention has been made about how to decide an input speech as the same speech. Further, if a complete coincidence of registered speech data with input speech data is use as a decision criterion, an enormous volume of data is required and it is almost impossible for even a telephone owner to generate a speech of a completely identical speech frequency.